There are a number of areas where aerial or surface trams are an important means of transporting products and materials. A particularly good example is in the mining industry where aerial trams are used to bring ore from mines located in mountainous areas to processing plants at lower more accessible levels. These tram lines may run for many kilometers and carry several hundred tram cars.
Steel wheels have traditionally been utilized on these trams. However, there are a number of problems associated with steel wheels which make some sort of synthetic thermoplastic or natural rubber compound wheels attractive. These include, for example, the fact that steel wheels are much more abrasive and cause much greater cable wear than do synthetic or natural rubber compound wheels. A further very distinct advantage of the non-metallic wheels is that there is cumulatively a very large weight saving in using these wheels, so that a smaller cable size can be utilized.
Unfortunately, very substantial problems have arisen in attempting to develop non-metallic tram wheels. The wheels are subjected to very high stresses because of the weight of the tram car and its contents, the substantial temperature changes frequently encountered, and the manipulation of the car at the ends of the line. These stresses have often resulted in cracking, chipping, breaking and delamination of the non-metallic wheel.
Where wheels have been developed using synthetic running surfaces, these have been composite structures comprising various metal and non-metal parts bolted together. Various causes of failure have been associated with these wheels.
No satisfactory solution has been forthcoming to these problems.
The present invention alleviates these problems by providing a unitary wheel structure which is capable of absorbing stresses from the various noted causes.